The empty cans need
to be quite strong and large, i find pineapple chunks particularly suitable.
The tins should be opened by the type of tin opener that doesn't leave
a sharp edge. Using a bradawl get your guardian to put a hole in each
side of the can. The holes should be at the bottom (Non opened) end of
the can. Measure the length of your legs then double that and cut 2 pieces
to this size. Thread the cord through the holes in the can and tie the
two ends together. If you are clever you can tie the knot so that it is
hidden in the centre of the can.

Hints:

Stand on the cans, pull
up tight on those strings and try not to fall over.